Re: [Qemu-discuss] Using vhost scsi

[Stefan Hajnoczi]

On Tue, Jul 26, 2016 at 06:35:30PM +0000, Yehuda Yitschak wrote:
> Thanks a lot for the detailed answer 
> 
> I managed to run virtio-scsi and i am benchmarking the performance
> 
> just curios, does virtio-scsi deliver about the same performance as 
> vhost-scsi ? 

Both virtio-scsi and vhost-scsi support many different configurations.
If achieving the best performance is critical then you need to benchmark
them yourself.

> i was surprised to learn that vhost-scsi isn't widely used.
> i thought vhost-scsi should be the favored solution since it should be faster 
> but i guess the features you mentioned are also a significant factor.

Since virtio-scsi is QEMU userspace code it poses a lower security risk,
is easier to update in sync with QEMU itself, and has all the QEMU block
layer features.  The performance of vhost-scsi and virtio-scsi should be
about the same - they both do the same thing and there's no great
advantage to a kernel thread vs userspace thread (they use essentially
the same functionality inside the kernel).

Stefan

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